Patent GB-1060348-A (GB)
Title: Improvements in or relating to glass-clad energy conducting devices
Inventor: HICKS JOHN WILBUR
IPC: C03B37/15
Filed: 1965-10-01
Abstract: A method of forming a fused energy-conducting device comprises the steps of placing longitudinally within a tube 12 (Figs. 4 and 5, not shown) of glass, a multiplicity of long and thin energy-conducting fibres 10 whose outer side surfaces are formed of glass, the fibres having undesired interstices therebetween, heating the combination 18 of said tube and fibres to a temperature sufficient to soften said tube and fuse together respective side surfaces of said fibres, and is characterized by the additional step of applying a high fluid pressure against the exterior of said heated tube and fibre combination wherein said pressure is of an amount sufficient to force said tube radially inwardly against said fibres to compress said fibres sufficiently to close the interstices and fuse the said surfaces of said fibres together into a unitary assembly.  The energy conducting fibres 10 may either have a metal core and a glass cladding or a glass core and a cladding of glass of lower refractive index but similar coefficient of thermal expansion.  The tube 12 should have a coefficient of thermal expansion very close to that of the glass claddings.  The fibres 10 are placed in a bundle within the tube 12 and the composite structure 18 flushed and washed out with a high purity solvent.  The combination 18 is then placed in a container 24 having inlets 56 and outlet 54 attached to two-way valves 64, 62.  A further inlet 40 allows for the introduction of the pressure fluid.  The assembly in its container 24 is located within a furnace 82 provided with electric heating coils 88 in the walls, the temperature being controlled by a thermocouple 90b activating a control box 90a. The temperature is raised to 350 DEG  F. to volatilize all the solvent which is drawn off down a vacuum line 68 from valve 62.  The temperature is then raised to between 800 DEG and 950 DEG  F. for several hours, whilst oxygen is fed from a supply line 74 and valve 64.  The oxygen causes any organic residue to be burnt off.  The oxygen may be drawn off down the vacuum line or along an exhaust line 66.  The temperature is then raised to 100 DEG  F. above the fusion temperature of the glass of the fibres 10 and tube 12 and a high vacuum applied to the combination 18 so that it is completely degassed. The temperature is then reduced to fusion temperature and the combination 18 flushed out with helium so that any residual gases are completely removed.  The helium is fed through a pipe 76.  The combination is then reconnected to the vacuum line and the best possible vacuum drawn therein.  At this time a fluid pressure of 1000 to 1500 p.s.i., e.g. of compressed air, is applied to the outer walls of the tube 12, through entry port 40, thereby compressing the tube 12 against the individual fibres which in turn are compressed against each other so as to close all interstices within the combination 18.  The resultant fused component 181 (Fig. 5) is then slowly annealed.  The final product 181 may then be cut up into individual small slices, or drawn out to form a composite fibre and the process repeated, or the individual slices may then be fused together as above.  The final product may be used in the face plates of cathode-ray tubes.